THIS INVENTION relates to tipping trailers and in a particular aspect to an improved method of means for stabilising such trailers particularly during the tipping thereof.
Tipping trailers have a number of different applications. In one application, tipping trailers are designed for carrying containers and the trailers are tipped to facilitate the containers being rolled onto or from a trailer. Tipping trailers however also have many other applications. The tipping trailers that are currently available are of a number of different designs including trailers having wheels mounted in a fixed position at the rear of the trailer bed. A disadvantage of tipping trailers is that they are relatively unstable when in a tipped position as the full load is taken by the axle of the rear wheel assembly only.
Trailers with increased load carrying capacity are fitted with three or more sets of longitudinally spaced wheel assemblies. Whilst this increases the load carrying capacity of the trailer in transit, the same difficulties referred to above are encountered when tipping the trailer is required.
The present invention aims to provide an improved tipping trailer which is stable in use during tipping. The present invention in a further preferred aspect aims to provide a tipping trailer that is typically longer than more conventional tipping trailers and therefore offers greater volumetric capacity. The present invention in yet a further preferred aspect aims to provide control apparatus for use in maintaining the stability of trailers during tipping. Other objects and advantages of the invention will become apparent hereunder.
The invention therefore provides a tipping trailer having forward and rear ends and a longitudinal axis and including a trailer bed, longitudinally spaced wheel assemblies for supporting the rear end of said trailer bed and pivotally mounted arm means coupling the trailer bed to the longitudinally spaced wheel assemblies characterised in that the arm means has a rearward pivotal connection and a forward pivotal connection such that as the trailer is tipped and said longitudinally spaced wheel assemblies remain in ground contact during tipping of said trailer bed with the load distributed evenly across the said longitudinally spaced wheel assemblies. xe2x80x9cTrailer bedxe2x80x9d is herein defined to mean any trailer section and includes but is not limited to flat beds, open topped and closed containers by way of non-limiting example.
The present invention thus provides in a first preferred aspect a tipping trailer including a trailer bed, a pair of longitudinally spaced wheel assemblies for supporting the rear of said trailer bed and pivotally mounted arm position control means for transferring load whereby said load is taken by said pair of longitudinally spaced wheel assemblies and said longitudinally spaced wheel assemblies remain in contact with the ground during tipping of said trailer bed with the load distributed evenly across the longitudinally spaced wheel assemblies. The pivotally mounted arm position control means, preferably comprises expandable and retractable arm position control means controlled to result in even load distribution.
Suitably the pair of longitudinally spaced wheel assemblies are mounted on a wheel carriage separate from the trailer bed or chassis and arm means connect the wheel carriage to the trailer bed. The arm means suitably is pivotally connected at one end to the wheel carriage intermediate the longitudinally spaced wheel assemblies of the pair and at their opposite end to the trailer bed. The arm means suitably extends rearwardly from its pivotal connection to the carriage for pivotal connection to the rear of the trailer bed. The arm means may be in the form of a main beam extending across the trailer bed above the longitudinally spaced wheel assemblies. Alternatively, the arm means may comprise arms on opposite sides of the trailer bed. The arms in this form may be interconnected.
The means for transferring load to the pair of rear longitudinally spaced wheel assemblies suitably includes ram means between the arm means and trailer bed. As the trailer bed is tipped, the ram means suitably are extended to maintain load through the arm means on both the rear longitudinally spaced wheel assemblies. Similarly when the trailer bed is lowered, the ram means are retracted. During these actions, the ram means also maintain the arm means in substantially the same position in space. The ram means preferably comprise one or more hydraulic rams. Suitably respective hydraulic rams may be provided on opposite sides of the trailer bed to extend between the arm means and the trailer bed.
The leading wheel assembly suitably remains in contact with the ground when the trailer bed is in its lowered position such that the load of, and/or carried, by the trailer bed is taken by the three or more longitudinally spaced wheel assemblies. When the trailer bed is tipped, the further wheel assembly is suitably lifted with the trailer bed from the ground.
Suitable suspension means are provided for the respective wheel assemblies. Preferably the suspension means comprise air suspension means. The air suspension means preferably comprise air springs suitably air bag means. The pair of rear longitudinally spaced wheel assemblies have respective axles which may be supported on respective suspension arms pivotally mounted to the wheel carriage. The air bag means are preferably provided between the free ends of the suspension arms and carriage. The further wheel assembly has an axle which may be supported on suspension arms pivotally mounted to the trailer bed. The air bag means for the further wheel assembly are preferably provided between the free ends of the suspension arms and trailer bed.
Most preferably, the air springs or air bag means of the air suspension means of the respective wheel assemblies are fluidly interconnected to equalise pressure to ensure even distribution of load across three or more axles of the longitudinally spaced wheel assemblies when the trailer is its lowered load carrying position.
For tipping of the trailer, the air bag means may remain inflated or alternatively, the air bag means may be deflated. Deflation of the air bag means provides a more stable tipping platform.
The present invention in a further aspect provides control apparatus for controlling the application of fluid to, or exhaustion of fluid from the ram means to resulting in the trailing longitudinally spaced wheel assemblies remaining in contact with the ground during tipping or lowering of the trailer bed. The control apparatus suitably includes first means for sensing directly or indirectly the position of the arm means relative to the trailer bed and means for applying fluid to, or releasing fluid from, the ram means if the sensed position does not correspond to a predetermined position.
The control apparatus suitably also includes further sensing means for sensing directly or indirectly the angular position of the trailer bed. The further sensing means suitably comprises means for sensing the angular position of linkage means connecting the trailer to a prime mover, relative to the trailer bed.
The control apparatus preferably compares the outputs of, or signals derived from, the first and further sensing means and if this comparison is not within predetermined limits, the control apparatus provides a control signal to cause hydraulic fluid to be supplied to, or exhausted from, the hydraulic ram means until the comparison is within predetermined limits. Supply of fluid to, or exhausting fluid from the ram means will extend or allow retraction of the ram means. The rate of supply or exhaustion of fluid is controlled in accordance with the compared angle signals to maintain the predetermined position of the arm means.
The first and further sensing means suitably comprise rotary or linear potentiometers however other forms of sensing means may be employed.